Convertible blower/vacuum units (blower/vacs) are in common use by homeowners and professionals for the removal of debris from yards, driveways, and sidewalks. A convertible blower/vac is a device which can be used as a blower and can be converted to operate as a vacuum.
In blower operation, typical blower/vac units provide a sweeping action created by the production of a fast moving stream of air from a rotating impeller within a housing. The impeller draws air into the housing through an air inlet. An air inlet cover permits air to enter the housing while at the same time preventing the entrance of foreign objects and debris. An air outlet on the housing directs the air stream to a removable exhaust or blower tube. A nozzle at the outlet of the blower tube is generally smaller than the outlet on the housing of the unit, thus causing a higher velocity air stream at the nozzle and allowing for greater precision and force in blowing debris across a surface.
Conversion from the blower mode to the vacuum mode typically requires removing the blower tube and placing a debris catching vacuum bag on the outlet. The air inlet cover is removed from the air inlet and replaced with a vacuum tube. In vacuum operation, the device draws air and debris through the vacuum tube. Debris is reduced (or "mulched") as it is drawn through the impeller. The debris is ultimately propelled into the vacuum bag for disposal.
Modern units are typically hand-held and, therefore, are made of lightweight materials and utilize lightweight power sources. The two most common power sources are electric and gasoline motors.
A high degree of efficiency of the air inlet cover and the impeller is desirable. An efficient air inlet cover and impeller system delivers a higher air horsepower output per given unit of power input to the motor. This is particularly advantageous with electric blowers where electric motor size may be restricted by the nominal AC power available (e.g., 120 volt, 12 amps). Because of this, simply increasing motor size is not always a practical solution for increasing the air horsepower of electric blower/vacs. Thus, efficiency improvements elsewhere are highly desirable. The present invention relates to improvements in both the air inlet cover and the impeller in order to increase blower/vac efficiency.
Many types of blower/vacs with novel inlets and impellers are known. For example, U.S. Pat. No. 5,601,400 issued to Kondo et al. on Feb. 11, 1997 and assigned to Nippondenso Co., Ltd discloses a centrifugal blower with a bell-mouthed inlet.
U.S. Pat. No. 4,694,528 issued to Comer et al. on Sep. 22, 1987 and assigned to The Toro Company discloses a portable electric blower/vac with an air inlet cover and an impeller driven by an electric motor. The air inlet cover includes a pressure ring for increasing the efficiency of the blower/vac when the cover is placed over the air inlet opening. The pressure ring increases the efficiency of the blower by reducing air spillover between the high pressure and low pressure sides of the impeller blades during rotation of the impeller.
U.S. Pat. No. 5,560,078 issued to Toensing et al. on Oct. 1, 1996 and assigned to The Toro Company discloses a portable electric blower/vac with a removable air inlet cover. The air inlet cover includes an integral pressure ring for reducing air spillover between the high pressure and low pressure sides of the impeller blades during rotation of the impeller. The air inlet cover also includes an adjustable choke member pivotally and concentrically mounted to the air inlet cover.
U.S. Pat. No. 4,674,146 issued to Tuggle et al. on Jun. 23, 1987 and assigned to Emerson Electric Company discloses a gasoline engine powered hand-held blower. The blower/vac includes an air inlet cover that provides a tortuous pathway for incoming air to reduce the likelihood of small rocks or pebbles being ingested into the impeller when the blower/vac is placed on a surface while the impeller is rotating.
U.S. Pat. No. 4,756,668 issued to Gassen et al. on Jul. 12, 1988 and assigned to Textron Inc. discloses a blower/vac apparatus with an air intake cover. The air intake cover includes a conical wall through which are defined a multitude of openings in direct communication with the air intake opening for the impeller.
U.S. Pat. No. 4,870,714 issued to Miner on Oct. 3, 1989 and assigned to Black and Decker Inc. discloses a portable electric blower/vac. The blower/vac includes an impeller with a plurality of blades. Each blade has an inner edge that slopes downwardly and away (as installed) from the hub of the impeller and an outer edge that slopes upwardly and away from a lowermost point of the inner edge. The inner and outer edges define generally conical surfaces of revolution. The outer edges define a generally outwardly facing concave surface of revolution.
U.S. Pat. No. 4,644,606 issued to Luerken et al. on Feb. 24, 1987 and assigned to McCulloch Corporation discloses a gasoline powered hand-held blower/vac. The blower/vac includes an impeller with a series of blades. Each blade includes an inner edge that slopes downwardly and away (as installed) from the hub of the impeller, a flat central section, and an outer edge that extends upwardly and away from the central section.
Fan Engineering Handbook, copyright 1983 to the Buffalo Forge Company discloses, on pages 2-36 and 2-37, a description of the coefficient of entry and the loss coefficient for a bell-mouthed entry to an air duct system. Pages 14-2 and 14-3 disclose further characteristics of the air flow entry conditions for a bell-mouthed entrance.
The present invention pertains to a portable blower/vac with a novel air inlet cover and impeller.